This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Projection televisions create video images by varying the color and shade of projected light. One example of a projection television system is a Digital Light Processing (“DLP”) system. DLP systems employ an optical semiconductor, known as a Digital Micromirror Device (“DMD”) to project video onto a screen. DMDs typically contain an array of at least one million or more microscopic mirrors mounted on microscopic hinges. Each of these mirrors is associated with a point on the screen, known as a pixel. By varying the amount of light that is reflected off each of these mirrors, it is possible to project video images onto the screen.
Specifically, by electrically actuating each of these hinge-mounted microscopic mirrors, it is possible to either illuminate a point on the screen (i.e., “turn on” a particular micromirror) or to leave that particular point dark by reflecting the light somewhere else besides the screen (i.e., “turn off” the micromirror). Further, by varying the amount of time a particular micromirror is turned on, it is possible to create a variety of gray shades. For example, if a micromirror is turned on for longer than it is turned off, the pixel that is associated with that particular micromirror, will have a light gray color; whereas if a particular micromirror is turned off more frequently than it is turned on, that particular pixel will have a darker gray color. In this manner, video can be created by turning each micromirror on or off several thousand times per second. Moreover, by shining colored light at the micromirrors instead of white light, it is possible to generate millions of shades or color instead of shades of gray.
Conventionally, there are two main techniques to produce the light used in a projection television or video projector. First, the light may be created by a conventional lamp, such as an incandescent lamp or a halogen lamp. Second, the light may be produced by one or more light emitting diodes (“LEDs”). There are many advantages to using LEDs instead of incandescent or halogen lamps. Specifically, LEDs are solid state components, and thus are typically more robust and more efficient than incandescent or halogen lamps, because they operate at lower temperatures. Moreover, because LEDs can generate specific colors of light, projection televisions employing LEDs do not use a color wheel. Unfortunately, a single LED cannot presently produce enough light to continuously project large video images, and conventional techniques for harnessing the light from multiple LEDs are extremely inefficient. An efficient method for harnessing light from multiple LEDs to project a video image is desirable.